The present invention relates to a method for producing pulp molded articles that can be used as, for example, packaging members such as containers and cushioning materials.
Plastics are used as general materials of packaging containers, for example, those with a lid and bottles, for their excellent molding properties and productivity. However, because plastic containers involve various problems associated with waste disposal, pulp molded containers formed by pulp molding have been attracting attention as substitutes for plastic containers. Pulp molded containers are not only easy to dispose of but economically excellent because they can be manufactured by using recycled paper.
The following process is known as one of the methods for producing the pulp molded containers. A pulp slurry is poured into a split mold, for example, a pair of splits, which has a plurality of holes interconnecting the outside of the mold to the cavity and which is lined with a metal net, and the split mold is evacuated from the outside to deposit pulp fiber on the metal net thereby to form a pulp deposited body. After the pulp deposited body is shaped in conformity to the configuration of the split mold cavity, a pulp molded container made of the thus shaped pulp deposited body is removed from the mold and dried.
In the above process, however, the pulp deposited body should be taken out while having a considerably high water content, or the pulp deposited body needs a long time for dehydration and drying. Therefore, the pulp molded container is liable to deformation, and productivity is low due to poor drying efficiency. As a result, the pulp molded container is uncompetitive in price.
Japanese Patent Application Laid-Open No. 133972/79 discloses a process for producing a pulp molded container which comprises ejecting a pulp slurry from a special nozzle into a net mold, blowing high-pressure air to remove a considerable part of the water content, followed by removal from the mold and drying with hot air, infrared rays, etc.
However, having no step of bringing the pulp deposited body into intimate contact with the mold surface (pressing onto the mold surface), the above process fails to make a complicated shape and involves great variations of precision in product shape and dimension. Moreover, the drying efficiency is poor, and the product wall thickness (basis weight or density) is uncontrollable.
Accordingly, an object of the present invention is to provide a method for producing a pulp molded article by which a pulp molded article of complicated shape can be obtained by integral molding with no seams at the mouth portion, the body, and the bottom portion.
The present invention has achieved the above object by providing a method for producing a pulp molded article comprising the steps of supplying a pulp slurry into the cavity of a mold composed of a set of splits, the set of splits being assembled together to form the cavity with a prescribed configuration, to form a pulp deposited body, feeding a fluid into the cavity to press the pulp deposited body onto the inner wall of the cavity thereby to dewater the deposited body, said pulp slurry containing pulp fibers having an average fiber length of 0.8 to 2.0 mm, a Canadian Standard Freeness of 100 to 600 cc, and such a frequency distribution of fiber length as comprises 20 to 90%, based on the total fiber, of fibers whose length ranges longer than 1.4 mm and not longer than 3.0 mm.